Gear Train
A gear ratio puzzle. The yellow driver turns at 60 rpm. Place gears so the marked output point turns at exactly the target ratio — and in the right direction.
Mesh gears from your inventory so the output spins at the target ratio and direction.
FreeOn this device
An ideal kinematic toy: pitch circles only, no friction, torque or tooth collisions. Upper-layer gears are blue.
Gears
| # | Teeth | Centre | rpm | Links |
|---|---|---|---|---|
| 12 (driver) | 8, 32 | 60 | — |
Solved on this device: 0 of 12. Ratios are exact fractions — no rounding.
Controls
- Choose a gear size from the inventory; every legal spot appears on the board and in a list of buttons.
- A spot either meshes with a placed gear or sits on the same shaft as one (upper layer). Tap a spot or its button to place the gear.
- Select a gear number in the table to remove it. Undo, Reset and Drive preview (which spins the train) are always available.
The rules
- Gears mesh when their edges just touch: the centres are exactly half the two tooth counts apart. Closer than that is an overlap and is refused.
- Meshing gears turn in opposite directions, and speed scales by tooth count: a 12-tooth gear driving a 24-tooth one makes it turn half as fast.
- Gears on the same shaft turn together. A loop that asks a gear to turn two ways at once locks the whole train.
Scoring, saving and limits
Solved when every goal point has a gear turning at exactly the target ratio and sign and nothing is locked. Ratios are kept as exact fractions, so there is no rounding.
Your gears, undo history and solved puzzles are kept on this device only. Download a backup to move them.
An ideal kinematic toy: external spur gears only, no friction, torque, backlash or tooth shapes. Each puzzle ships with a layout known to reach its goal.
Questions
- What does an idler gear do?
- An idler between two gears reverses the direction of the output but leaves the overall ratio unchanged.
- Why is my train locked?
- An odd loop of meshing gears — three gears all touching, for example — cannot turn at all. Remove one to break the loop.
- How do compound shafts help?
- A small and a large gear on one shaft turn at the same speed but drive their neighbours at different ratios, so you can multiply ratios in a small space.